Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Cameron Roxberry
Over 70% of the worlds freshwater is in the form of glaciers. Currently 10% of
the world's land mass is covered in glaciers - that's 15,000,000 sq km, but
during the last ice age glaciers covered 32% of land. Glaciers have formed and
receded for the duration of earth’s history. From the first ice age until now,
glaciers have changed and affected the worlds landmasses as well as the oceans.
A third of the world population is supported by the fresh water from glaciers.
(facts From: http://jove.geol.niu.edu/faculty/fischer/429_info/429tr)
Glaciers are seasonal in nature. Glaciers store water through one
season, and releases water during another. This cycle is not only important for
human use, but also for plant growth and animal migration. Due to the fact that
glaciers are affected by long term climate change, glaciers are studied and
watched closely largely for climate change indicators. Small changes in size
from year to year are monitired and help map out global warming charts, as well
as indications change over time.
Glaciers are formed when the accumulation of snow and ice surpasses the
ablation. As the weight of the snow and ice increases it finally begins to move.
Year after year from the thawing and freezing of ice, the glacier begins to take
shape and mold the landscape around it. Glaciers have less dense ice from the
direct freezing of water under the glacial mass. The air between snowflakes is
trapped and the bubbles crate pockets of air in-between the ice.
Once glaciers are formed they are in a constant state of movement until gone.
The beginning of the glacier is called the glacier head, and where the glacier
is ended is called the glacier foot. The glaciers move over the land that is sat
on because of the presence of liquid water.
As the pressure increases toward the base of the glacier, the melting point of
water decreases, and the ice melts. Friction that is caused from the movement
of the ice also contributes to the melting of the glacier. Friction also makes
the bottom of the glacier move slower than the top.
As the glacier moves along its path, it picks up and carries geological
structures such as rocks and sediments. When glaciers move through landscapes it
causes what is referred to as glacier valleys. This is where the glaciers have
carved a large crevice into the surrounding mountains or terrain. The rocks that
are picked up and frozen into the bottom of the glacier act as grit in
sandpaper. Glaciers are also studied in past geology. By tracking where the ice
sheet formed and to where it dropped all of the sediment, scientists can tell
past geological conditions and terrains. Rocks that are found at the end of
glaciers are sometimes hundreds of miles from rocks similar in nature.
During normal formation of valleys, water normally forms valleys in the
shape of a V. In the formation of glacier valleys, ice creates more of a U
shape. Glaciation cause the valleys to be deeper, glaciation also causes the
valleys to become smoother due to erosion. Once glacier plucking has occurred
and the ice sheet has receded, often small mountain lakes form in the left over
crevices called tarns. The terrain the glaciers were once formed will forever be
changed due to it. Lakes and geological structures are altered and changed.
Glaciers have been and continue to be very important in the formation of earth
as well as other planets. Without them, valleys, lakes, mountains and our way of
lives would be drastically different.
Since first documented in 1850, glaciers have been recessing; meaning that fresh water supplies in many countries will dwindle. Long term effects of this can go as far as changing levels of the ocean. Even with small change can drastically buts ecosystems into distress. Some scientists and glaciologists have linked this directly to global warming, although this theory is still not proven. The human population as a whole needs to realize just how important and crucial glaciers are to the survival of not only a country, but a world population. Glaciers also act as a mirror reflecting harmful UV rays back into space. So with the melting of glacier due to temperature rise, a snowball effect will take place and global temperature will continue to rise at a more alarming rate.
"Glaciers." 301 Moved Permanently. Web. 25 Apr. 2012.
"Service Interruption." All About Glaciers, Introduction. Web. 25 Apr. 2012. http://nsidc.org/cryosphere/glaciers/index.html
Weller, Roger. "Glaciers." Glaciers. Cochise College. Web. 25 Apr. 2012. http://skywalker.cochise.edu/wellerr/GLGP-illvocab/GLGP-12.htm